Saving energy is an increasingly important topic with respect to the continuously increasing energy demand of earth's population and with respect to environmental conservation. In addition to a responsible handling of energy consuming devices and installations, saving energy comprises also measures for the devices themselves. For example, energy is saved by automatic switch off of devices if they haven't been used for some time. In other cases, like e.g. in case of heating systems, energy is also saved by an effective thermal insulation of the rooms to be heated. In case of devices being operated with fuels, energy is saved amongst others by computer-controlled fuel supply, like e.g. injection systems, etc.